Telephonic receiver and circuit



2' Sheets-Sheet 1.

(No Model.)

W. MARSHALL.

TELEPHONIG RECEIVER AND CIRCUIT.

N0. 341,259. Patented May 4, 1886.

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(No Model.) 2 Sheets-Sheet 2.

W. MARSHALL.

TELEPHONIG RECEIVER AND GIRGUIT; v No. 341,259. V Patented May 4, '1886.

WITNESSES am lA/VE/I/TOI? wan /%MMZ WW 7 I A By Afforney N. PETERS. Hmo-uma mi, wishin m". DJ}.

UNITED STATES WVILLIAM MARSHALL,

PATENT OFFICE.

on NEW YORK, N. Y.

TELEPHONIC RECEIVER AND CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 341,259, dated May 4, 1886.

Application filed February 6, 1885. Serial No. 155,159.

To aZZ whom it may concern.-

Be it known that I, WV LLIAM IVIARSHALL, of the University Building, in the city and State of New York, have invented certain Improvements in Telephonic Receivers, Apparatus, and Circuits for Telephonic Communication, of which the following is a specification, reference being had to the accompanying drawings, in which Figures 1, 2, and 3 are diametrical sections of the various forms which I have given to my invention. Figs. 4, 5, and 6 are diagrams showing the circuits in which my improved receiver is preferably used, and Figs. 7, 8, 9, 10, and 11 are views of details of construction.

My telephone receiver may be used with the ordinary transmitter, is constructed on the general plan of what is known as a condenser, and consists of a pile of leaves of tin-foil or other suitable substance with insulating material interposed, the whole preferably perforated and in the middle and placed in layers pressed together at the outer edge.

Fig. 1 shows one form, consisting of a case, A, provided with perforated covers B B, the covers having screw-threads, which construction serves to regulate the amount of compression brought to bear upon the outer part of the condenser-pile. Every second leaf of the tin-foil is connected to the binding-post 0, and every other leaf to the binding-post d. Above and below the condenser pile are placed washers K K. All the parts being introduced into the case, the cover 13 is put in place and screwed down by turning it until a degree of compression is produced at the circumference of the condenser-pile to produce a suflieient bulging of the middle part of the condenser to be relieved from pressure, when its speaking-powers will be clear.

Instead of washers, the cover may have an annular projection around its inner face. (Shown in Fig. 11.)

To further improve its speakingpowers, I sometimes cause more than onehole to be made extending through the substance of the pile that is not under pressure. In the drawings,

Figs. 1, 2, and 3, one such hole is shown in the center and extending quite through the pile. I also, to prevent contact between the alternating sheets of tin-foil, generally make the holes in them a little larger than the corre- No model.)

sponding holes in the paper, and make the disks of tin-foil smaller than the disks of paper, as shown in Figs. 7 and 8.

Fig. 2 shows a telephone-receiver the condenser of which is constructed of two long pieces of tin-foil or other suitable conducting material, (shown by the full lines a a,) with paper or corresponding insulating material (shown by the cross-hatched lines b b) interposed between them. The leaves of foil are connected at their opposite ends to four bindingposts, 0 d ef. At the bends of the condenser the insulator and plates are nearer together than at the middle from the bends, and this acts as if it were under greater pressure at the edge.

Fig. 3 shows the receiver provided with a resistance-coil, 0, contained within the case and provided with binding-posts g h. The terminals of the resistance-coil can be connected to posts (I c, for the purpose of shunting the condenser, especially when used on single or ground lines. One form of such resistancecoil is shown in Figs.'9 and 10. y

In Fig. 4 the receiver is connected in multiple are in the primary circuit. In it D i11- dicates a transmitter, F the receiver, G a battery, and E a resistance-coil. The circuit may be grounded at as w.

Fig. 5 shows another way of shunting the receiver with a resistance-coil, instead of putting the resistance coil or shunt in the receivercase proper.

Fig. 6 shows a circuit analogous to that shown in Fig. 4., except that a local microphonic circuit is introduced, and the receiver F is placed in multiple are upon the secondary circuit.

In the drawings, G represents a battery on the primary circuit; G, a battery on the secondary circuit or line; E, a resistance-coil, and D a transmitter. a" no show where theline may be grounded, if desired.

The resistance coils or shunts used for shunting the receiver should have a high resistance, and the resistance should be proportionate to the resistance of theline. For instance, on a line of two thousand oh ms the shunt may have five thousand to siX thousand ohms.

WVhen a proper amount of pressure is brought to bear on any one part of the condenserpile, leaving the other part very loose, and

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especially those parts near the perforation, then the condenser speaks the best, because the condenser-plates, being statically charged by the line-battery, are able to vibrate when an extra or secondary current is induced in the line and modifies the static charge of the condenser.

\Vhat I claim as my invention, and desire to secure by Letters Patent of the United States, 1s-

1. The receivingteleph one herein described, consisting of a condenser perforated through its leaves, with a shunt shunting the said re; ceiver.

2. A receiving-telephone consisting of a shunted condenser which is normally charged by a constant current on line, and current varying devices located at the transmittingstation in a primary or transmitting circuit and adapted to vary the statical condition of the normally-charged receiver, and thereby reproduce articulate speech and other sounds which actuate the transmitter.

3. A receiving condenser-telephone located in a normally-charged secondary circuitextending to a transomitting-station, in combination with a high-resistance shunt around said condenser and a local primary circuit to said secondary circuit located at the transmittingstation and containing current varying de vices, substantially as described.

4. A condenser-telephone located in a normally charged secondary circuit extending from the transmitting to the receiving station, in combination with a shunt around said condenser and eurrentvarying devices located in an independent circuit at the transmittingstation, whereby any variation in the current in said independent circuit creates a change of stati cal condition in the receiver and causes it to reproduce the'sounds which cause said current variation, substantially as described.

W'ILLIAM MARSHALL.

Vitnesses:

THos. H. FLAHERTY, WILLIAM F. ERVING. 

